Process for making hydrocarbonlead compounds



Patented Dec. 26, 1950 PROCESS F1313. MAKILI G HYDRGCARBON- LEADCOIVIPOUNDS George Calingaert and Hymin Shapiro, Detroit, Mich,assignors to Ethyl Corporation, New York, N. Y., a corporation ofDelaware No Drawing.

Application December 24, 1949,

Serial No. 135,021

(Cl. 260 i-37) 7 Claims. 1

This invention relates to a process for the manufacture ofhydrocarbon-lead compounds, particularly alkyllead compounds. Morespecifically our invention is directed to an improved process for themanufacture of tetraethyllead.

The process employed in present commercial practice for the manufactureof tetraethyllead has been in use for a number of years and, in general,is satisfactory. However, it has certain disadvantages which areovercome by practicing our invention. The present commercial processproceeds by reacting a sodium-lead alloy of composition controlled tocorrespond substantially to NaPb with ethyl chloride according to theequation:

With the highest yields obtained thereby, only about 22 per cent of thelead present in the Nal b alloy is converted to tetraethyllead. Underconditions of best operation no one heretofore, as fair as we are aware,has been able to increase this yield of tetraethyllead by even a few percent. due to the inherent limitation in yield as is apparent fromconsideration of the above equation. It should be noted that in thisreaction at least 75% of the lead originally employed is not alhylated.Thus in this reaction, large quantities of lead must be recovered andreprocessed to NaPb alloy in order to make it economical. A furtherdisadvantage of such a large quantity of unreactcd lead is that valuablreaction space in the reaction vessel is occupied by materials which areessentially inert for the manufacture of tetraethyllead under presentconditions and mode of operation.

Various other processes for the production of alkyllead compounds havebeen described in the literature. For the most part, however, theseprior art methods are subject to the same disadvantage that very largeamounts of the lead alloy or lead salt entering into the reaction areconverted to free lead instead of the desired alkyllead compound. knownGri-gnard reaction has been suggested frequently for the manufacture ofthese cor pounds, as exemplified b U. S. Patents Nos. 1,765,723;1,798,593; 1,805,756; 1,863,451; 1,949,- 948, and other United States orforeign patents of a similar nature. It is evident from a considerationof the equation for the Grignard reaction that a maximum of-5ll% of thelead in the lead chloride can be converted to tetraethyllead;

For example, the well-- While the above patents attempt to improve theefficiency of the Grignard reaction upon which they are dependent, theyare all subject to the disadvantage that even though the yieldapproaches the theoretical, 56% or more of the lead which enters intothe reaction is not converted to alkyllead but is left as free lead.

Further, the free lead produced in the (irisnard reaction will not reactwith additional quantitles of C2I'I5MQC1 and thus it must be recovered,purified, and ii reused, converted to lead chloride. This is tedious,expensive and inefficient. In part, it accounts for the fact that, sofar as we are aware, the Grignard reaction has never been applied to anyextent commercially to the production of tetraethyllead or any otherorganic lead compounds. Despite its drawbacks, therefore, the presentcommercial operation is a more efiicient and desirable process than anybased upon the Grignard reaction, due in part to the high cost of leadchloride and the expense involved in reconverting the free lead to leadchloride.

It is therefore an object of our invention to provide a process for themanufacture of alkyllead or aryllead compounds which overcomes the aboveobjections to the present commercial process and which is far superiorto the Grignard process. Particularly it is an object of our inventionto increase the conversion of lead to tctraethyllead above that obtainedin the present commercial practice. Another object of our invention isto increase th product output of tetraethyllead using the existingequipment of the present commercial process. It is a further object toproduce tetraethyllead and related compounds by a process which canconvert more of the lead charged to the reaction into the desired endproduct, thereby avoiding the expensive reprocessing of large quantitiesof lead.

We accomplish these objects by reacting lead such as the lead producedin the present commercial process with an elkylating or arylating agentsuch as an alkyl chloride and an alkyl- 01' arylmagnesium halidecorresponding to the general formula RMgi Inaccordance with ourinvention, we have found that to produce alkylor aryllead compounds itis unnecessary to start with either a lead alloy, such as thesodium-lead alloy used in the present commercial process, or with a leadsalt such as lead chloride, as in the Grignard process. On the contrary,our invention is in the surprising discovery that hydrocarbon-leadcompounds can be made by reacting free lead with an alkylating orarylating agent and a compound correspondin to the general formula RMgX,in which R is a hydrocarbon radical and X is a halide. A typicalreaction of our process may b expressed by the following equation:

in which, for example, R may be ethyl and X may be chlorine.

It should be pointed out that free lead will not react with RMgX alone.Both the RMgX and RX type of reagent are needed in our process ascontrasted with the Grignard reaction in which lead chloride will reactwith an ether solution of RMgX with no RX present.

By practicing our invention, yields of over 90 per cent based on thelead charged to the reaction zone have been obtained. Thus, more than afourfold increase in yield of alkylleads over the present commercialprocess and almost a two-fold increase over the Grignard process areobtainable by practicing our invention. Such a yield improvement isremarkable and as far as we are aware such high efficiencies in the useof the lead charged are not shown in any of the processes described inthe literature, and have not been obtained by the present commercialprocess.

The lead used in the process of our invention is any form of metalliclead. which from its physical state, degree of comminution, andconditions of surface is reactive with an alkvlating or arylatin agentand an alkvlor arylmagnesium halide to produce an alk lor aryllead. Ingeneral the lead should be finely divided and its surface s ould be freefrom oxidation, which would decrease its activity. It is to be notedthat substantial yields of tetraethyllead have been obtained in ourrocess from an oxidized form of lead. Ho ever. the removal of, or theprevention of the formation of oxidized material on the lead urfacematerially increases the yield obtainable. The unreacted lead remainingfrom kno n processes in which some alkyllead is formed is an especiallyexcellent form of lead for use in our invention. For example, theunreacted lead remaining from the present commercial process, whentreated according to our inv ntion with ethyl chloride. andethylmagnesium ch oride. results in a yield of about '79 per cent ofalkyllead based on the unreact d lead c ar ed. Thus based on the aboveactual yield, the lead efliciency, i. e. utilization of the lead inconverting it to an alkvllead, is almost 50% greater than thattheoretically possible for the Gri'rnard reaction.- Based on actualyields obtainable by the most careful control of the Grignard reaction.the lead efliciency in our process is almost 100% greater.

Further examples of lead which can be succe sfully employed in ourprocess include lead powders resulting from the decomposition oforgano-lead compounds by heat, such as for instance, the lead depositedduring the thermal decomposition of organo-lead compounds. Certain otherforms of lead powders which are sunlciently active for use in makingtetraethyllead by our process can be prepared by grinding or otherwisecomminuting lead metal or massive lead especially when this is done inan atmos phere of nitrogen or under an appropriate liquid, whichprevents the oxidation of the lead surface. A further example of amethod of preparing a finely divided lead suitable for practicing ourinvention is the reductive precipitation of lead from its compounds.Other methods such as electrolytic deposition will occur. to thoseskilled in the art.

Lead alloys, particularly allows containing alkaline earth and alkalimetals, are also a good source oflead and have been successfullyemployed. Sodium-lead alloy is an especially good alloy for such use.Other examples of metals alloyed with the lead which can be successfullyused in practicing our invention are calcium,

potassium, and magnesium. In general any al- 10y which will react in thefollowing equation can be employed as a source of lead for our process:

Metal-lead alloy-l-ethyl chloride=tetraethyllead+lead+metal chloride Ourinvention is adaptable to the production of alkyllead, aryllead or mixedalkylaryllead compounds generally, such as tetraethyllead,tetramethyllead, dimethyldiethyllead, triethylphenyllead,tetrapropyllead, and tetraphenyllead. Nevertheless, for convenience indescribing our invention hereafter, specific reference will be made totetraethyllead, the most widely known because of its u e as anantiknock. Whenever in the following description this material isreferred to it is to be understood that othe alkyl or aryllead compoundsor mixtures can be made by our process.

Generally the process of our invention is conducted as follows: lead.for example in the form of sodium-lead alloy, NaPb, is first placed in areaction vessel such as the autoclave of the present commercial process.The alkylmagnesium halide may also be added at this time although it ispreferable to add it after the reaction vessel is closed. The vessel isthen closed exce t for the liquid feed line through which the fluidreactants are passed and a line to a reflux condenser. The necessaryquantity of alkylat-- ing agent such as ethyl chloride is thenintroduced into the autoclave followed by delivery of the alkylmacnesiumhalide such as ethylmagnesium chloride, or the latter can be added alongwith the ethyl chloride. In the former method, if the lead is introducedin the form of sodium-lead alloy, the ethylmagnesium chloride is addedafter the customary reaction between the alloy and the alkylating agentis initiated. In one preferred modification of our invention thealkylmagnesium chloride is not added until most of the customaryreaction between the alloy and the'alkylating agent has occurred. Inboth methods of operation a dual proce s is occurring, namely thecustomary reaction between the sodium-leadalloy and the ethyl chloride,and the reaction of the free lead formed in such reaction withadditional ethyl chloride and the ethylmag ne ium chloride.

Thus, the preferred methods of operating our process using a lead alloysuch as sodium-lead alloy, are the method of reaction wherein thealkylmagnesium halide is added prior to or concurrently with thealkylating agent, hereinafter referred to as the one-stage process, andthe method wherein most of the alkylmagnesium halide along withadditional quantities of alkylating agent is added after the customaryreaction is substantially completed, hereafter referred to as thetwo-stage process. Of course, variations in the above modifications canbe made such as introducing part of the alkylmagnesium halide along withthe initial feed of the alkylating agent followed by additionalalkylmagnesium halide after most of the customary reaction has occurred.Also while it is preferable in our twostage embodiment to add only theamount of alkylating agent usually employed for the first stage and thenadd the amount required for the second stage, it is within the scope ofour invention to add most of the alliylating agent in the first stageand primarily only the alkylmagnesium halide in the second stage.Further, while the above general description of our process as well asthe detailed examples which follow are descriptive of a batch-tymoperation, it is to be understood that the process of our invention mayalso be conducted in a continuous manner wherein the lead and theallzylation or arylat ing agent and the hydrocarbonmagnesium halide arebrought together continuously in any suitable reaction zone.

Unless otherwise stated all parts and percentages herein are by weight.Further in the following examples, ether refers to diethyl ether unlessotherwise specified.

Our invention can be further understood by referring to the followingillustrations of detailed working examples:

EXAMPLE I (Two-stage reaction using sodium-lead alloy and ethylchloride) A charge of 100 parts of NaPb alloy was added to a reactionvessel equipped with an agitator, a jacket for circulation of heating orcooling liquids, a reflux condenser, charging and discharging ports,liquid feed'lines, and means for releasing the pressure. Liquid ethylchloride in the amount of 167 parts was added under pressure to thestirred solids in the vessel over a period of one-half hour. Bycontrolling the flow of liquid in the autoclave jacket and in the refluxcondenser the temperature of the reaction mass was permitted to risefrom an initial temperature of 50 C. to a temperature of 70 C. duringthis feed period. The pressure in the autoclave during this feed rose to75 pounds per square inch gauge where it was maintained. The temperatureof the stirred reaction mixture was maintained at 70 C. for anadditional minutes maintaining the 75-pound pressure. While the aboveoperation was carried out, 15.7 parts of magnesium chips were placed ina separate reaction vessel equipped with an agitator, a jacket for circuating heating or cooling liquids, reflux condenser, liquid feed lines,solid feed means and lines for providing an inert atmosphere andcontrolling the pressure. A mixture of 4 parts of ethyl chloride and 2parts of diethyl ether was added all at once to the magnesium at atemperature of C. in the closed reaction vessel. After five minutes ofagitation, 93.8 parts of ether was added at a temperature of 25 C. overa period of 10 minutes, followed by 37.7 parts of ethyl chloride addedover a period of one hour, during which time the temperature variedbetween and C. and the pressure was maintained between a pressure of 30to 40 pounds per square inch gauge. After the addition was complete,agitation was maintained for an additional 90 minutes. At the end ofthis period the thus formed solution of ethylrnagnesium chloride inether was transferred by nitrogen pressure to the autoclave of thealkyllead reaction through a line connecting the two vessels. The ethylchloride added at the beginning of the first stage, which was in excessover that required to alkylate the sodium-lead alloy in the first stage,remained for further reaction in the secend stage. The autoclave wasmaintained at a temperature of C. and a pressure of approximately 130pounds per square inch gauge for an additional minutes. At the end ofthis period the pressure in the autoclave was reduced to atmospheric byventing for 1-5 minutes while the temperature was maintained at 70 C.For an additional period of 15 minutes at 70 C. nitrogen was passed overthe reaction mass with the autoclave open to the atmosphere. The masswas then cooled to 45 C. over an additional 30 minute period whileflushing with a stream of nitrogen. The reaction mass was thendischarged to a steam-still containing 250 parts of water. With C. steamfed to the jacket of the steamstill, a forecut of ethyl chloride andether was taken, up to a vapor temperature of 70 C. At'

this point the steam jets were turned on, and with the jacket steam off,the tetraethyllead was distilled for one and one-half hours after thefirst drop of tetraethyllead appeared in the dis-- tillation receiver.The yield of product was 117 parts, or a yield of 83.5 per cent based onthe lead present in the sodium-lead alloy.

EXAMPLE II (One-stage reaction using sodium-lead alloy and ethylchloride) Using substantially the same operating procedure as describedin the above detailed example, a one-stage modification was carried outwith the variation that the other solution of ethylmagnesium chloridewas added simultaneously with the charge of ethyl chloride to thealkyllead autoclave containing the sodium-lead alloy over a perind of415 minutes. In this process 100 parts of sodium-lead alloy, 167 partsof ethyl chloride, 57.4 of ethylmagnesium chloride and 95.9 parts ofether were employed. The operations of cooking, venting, cooling,discharging and recovery of the product were conducted substantially asabove. The yield of product was 66.7 parts, or 47.5 per cent based onthe lead present 5 in the sodium-lead alloy.

EXAMPLE III The process of Example I was carried out until the reactionbetween the ethyl chloride and the sodiumdead alloy was substantiallycomplete, that is after the cooking period of 15 minutes at atemperature of 76 C. was completed. The autoclave was then vented toatmospheric pressure over a period of 15 minutes with the agitator in a.motion and the temperature maintained at 70 (3., thereby removingsubstantially all the unreaoted ethyl chloride. A solution of 57.4 partsof ethylmagnesiurn chloride in 95.8 parts of ether and containing anadditional 167 parts of ethyl chloride was then added to the autoclaveduring a period of 45 minutes. The operations of cooking, venting,cooling, discharging and recovery of the product were conductedsubstantially as in Example I above. The yield of product was 117 parts,or 83.5 per cent based on the lead present in the sodium-lead alloy.

EXAMPLE IV In place of the sodium-lead alloy of the fore- '"I goingexamples 168 parts of a lead powder were added to the autoclave and 250parts of ethyl chloride, and 85.7 p rts of ethyl magnesium chloride in143 parts of ether were added in the sequence and under the conditionsof Example II. The additional operations of cooking, venting,

cooling, discharging and recovery of-the product were conductedsubstantially as in Example I above. The yield of product was 109 parts,or 77.8 per cent based on the lead metal charged.

Various alkylating and arylating agents can be employed in ourinvention. In general the alkylating and arylating agents of our processare organic compounds which may be represented by RX, having the desiredalkyl or aryl group, R, attached to a negative atom or radical, X,capable of reacting with the magnesium of the hydrocarbon-magnesiumhalide to form the corresponding magnesium salts, MgXz, as shown in theabove equation for a typical embodiment of the process of our invention.For the most part these alkylating and arylating agents are esters ofinorganic acids such as the alkyl and aryl chlorides, bromides, iodidesand phosphates. In general the inorganic acid ester alkylating andarylating agents are the monochloro, -bromo and -iodo derivatives of theparafiin and aromatic hydrocarbons such as methane, ethane, propane,butane, pentane, and benzene and the corresponding trialkyl phosphates.For example methyl chloride, methyl iodide, ethyl chloride, ethylbromide, ethyl iodide, n-propyl chloride, n-butyl chloride, n-butylbromide, n-amyl chloride, n-amyl iodide, phenyl bromide and triethylphosphate can be successfully employed. Instead of the normal alkylhalides, other isomers such as the iso compounds can be used. Variouscombinations of these alkylating agents can also be used. For exampletwo or more alkylating or arylating agents can be used simultaneously inthe oneand two-stage process or different alkylating or arylating agents.can be used in each stage of the two-stage process.

The different alkylating and arylating agents mentioned above do not allbehave in the same manner. Th operating conditions can be varied withinthe scope of our invention in order to obtain the best results with thepatricular alkylating agent or agents employed. For exam le, exce t formeth l chloride, the lower alkyl chlorides, particularl ethyl chloride,give excellent yields of tetraalkyll ad in both the one! and twostageoperations with sodium-lead a loy. However. methyl chlorid and t e alkvlbromid s and iodides are preferably em loyed in the second step of thetwo-st e operation since better yields are thereby obtained.

In general, the alkylating agents which are well known for use in thepresent commercial process, or hich can he used in our rocess with alead alloy, ive xcellent results wh n em loyed in all em od ments of ourinvention. Those alkvlating or arylating ag nts which give relativelylow yields in the present commercial process, or in our process in whicha lead alloy is em loyed, do, however, give excellent results when freelead orthe lead resulting from the roces es ofthe prior art are emloyed, or are em loyed in the second stage of the two-stage embodimentof our invention. re ard es of the form in which the lead is em loy d inthe first stage.

For best results, the alkvlating and arylating agents of our process shold be employed in excess over the amount required according to theequation for our reaction as given previously herein'. If less than theamount of alkvlatingagent reouired to completely alkyl te the leadaccording to the above equation of a typical example of our pro e s isused. the yields will be lower, but will still be good when determinedon the ba is of the amount of alkylating agent. This is especially truewhen the two-stage operation is employed and in an operation wherein thealkylat ing agent is fed to the system gradually in a batch orcontinuous operation.

5 The hydrocarbon-magnesium halide of our process, illustrated by theRMgX in the above typical equation of our process, consists of thedesired alkyl or aryl radical, R, and a halide, X, selected fromchlorine, bromine or iodine. Thus, for example, we can employ in theprocess of our invention ethylmagnesium chloride, ethylmagnesiumbromide, ethylmagnesium iodide, methylmagnesium chloride,rnethylmagnesium bromide, methylmagnesium iodide, n-propylmagnesiumchloride, n-propylmagnesium bromide, n-butylmagnesium chloride,n-butylmagnesium bromide, n-butylmagnesium iodide, phenylmagnesiumchloride, phenylmag-nesium bromide and phenylmagnesium iodide, preparedby reacting ethyl chloride, ethyl bromide, ethyl iodide, methylchloride, methyl bromide, methyl iodide, n-propyl chloride, n-propylbromide, n-butyl bromide, n-butyl iodide, phenyl ch oride, phenylbromide and phenyl iodide respectively with metallic magnesium. Insteadof the hydrocarbon-magnesium halides prepared by reacting normal alkylhalides with metallic magnesium, other isomers can be employed such asthose derived from the iso and secondary alkyl halides. Variouscombinations of hydrocarbon-magnesium halides can also be used.

Any of the usual solvents or cata ysts normally employed in thepreparation of hydrocarbonmagnesium halides can be successfully employedin preparing hydrocarbon-magnesium halides for use in the process of ourinvention. Examples of such solvents which can be employed include theali hatic ethers such as diethyl ether, methyleth l ether, dipropylether and dibutyl ether, the aliphat c ethers o the olyhydroxv alcoho s,such as the dimethyl ether of eth lene glycol, and various amin s suchas triethvlamine, aniline, dimethylaniline and diphenylamine. We havealso found that various catal st. or reaction starters, such as iodineor mercury, often employed to initiate the reaction between the organichalide and the ma nes um, do not interfere with the subsequent use of thh drocarbon-magnesium halide in t e ro ess of our invention.

The hydrocarbon-magnesi m halide employed in our in ent on can be preared by any one of the wel -known methods. For example, in one e bodient o o r in"ention the hydrocarbonmagnesiurn. hal de can be prepar d bythe addition to m nesium r et l of a sol tion of an organic h l de indiethyl eth r. and allo ing reaction to take pl ce u til all themagnesium is re acted and dissol e therein, a d then adding this soution. of hydrocarbon-magnesium halide in ether to t e other re ctantsof our invention in the manner describ d her tofore. In a further embodient o our invention, the ether or other solvent or catalyst emp o ed inthe reparation of the hvdrocarbommagnesium halide may be removed byevaporat on and the resulting so id reaction pro uct em loyed in the proess of our invention. Th s, we have found that the amount of et er orsolvent commonly employed in the manufacture of the hdrocarbon-magnesium 0 halide is not critical and we have obtainedexcellent results with h drocarbon-magnesium halides either disso ved inappropriate solvents or as a dry solid. Furthermore, it is sometimesconvenient to intro uce the hydrocarbon-magne ium 75 halide to thereaction zone as a slurry, and for this purpose the solvent and excessorganic halide is only partialy evaporated until thehydrocarbon-magnesium halide begins to separate from solution. Thus,depending on the type of operation, that is batch, semi-continuous, orcontinuous the amount of solvent or carrier liquid can be varied so asto produce the most efiicient operation. Thus in the two-stageembodiment of our invention described in.Example I We have employed,along with the 100 parts of sodiumlead alloy and 167 parts of ethylchloride of the first stage, 57.4 parts of ethylmagnesium chloride with22.4, 95.8, 192 and 287 parts of ether and obtained yields of alkylleadproduct of 56.6, 112, 92.1 and 66.6 parts respectively or 40.3, 83.5,65.6 and 47.4 percent based on the lead in the sodiumlead alloy.

We have, however, found that for the successful operation of the processof our invention the hydrocarbon-magnesium halide can be prepared in thecomplete absence of the ether or other activating solvent usuallyassociated with the preparation of these compounds. Further, theaddition of such solvent to the hydrocarbon-magnesium halide prepared inits absence is likewise not necessary for the successful operation ofour process. For example, we prepared ethylmagnesium iodide by treatingpowdered magnesium with ethyl iodide dissolved in benzene containing atrace of iodine. After reaction, the benzene and excess ethyl iodidewere removed, leaving a dry, free-flowing gray powder, which wassuccessfully employed in the process of our invention as follows: To theresidue remaining in the autoclave after the reaction of 100 parts ofsodium lead alloy with 167 parts of ethyl chloride according to theprocedure of Example III, was added 140.4 parts of the above-describeddry ethylmagnesium iodide and 252 parts of ethyl chloride. After theoperation of cooking, venting, cooling and discharging, the yield ofproduct was 65.8 parts or 46.9 per cent based on the lead in thesodium-lead alloy.

The process of our invention is not limited to the preparation oftetraalkylead or tetraaryllead compounds in which each of the four alkylor aryl groups attached to the lead atom is the same, as intetraethyllead or tetraphenyllead, but also includes the preparation ofmixed alkyllead compounds, mixed aryllead compounds and mixedarylalkylead compounds. Thus we may illustrate a typical generalizationof the process of our invention by the following equation:

wherein each of a, b, c, d, and e is a number between and 1 inclusiveand the sum as are capab e of forming magnesium salts with the magnesiumof the hydrocarbon-magnesium halide, as for example the phosphateradical.

It should be pointed out that in the above typical general equation forour proc ss the use of a catalyst is not mentioned. The hydroparts ofether.

10 carbon-magnesi m halide is prepared in the usual way, involving 'seof an activating solvent and catalyst No f rth-r qrantit es of catalystor activating sol cuts are required for the successful operation of onprocess, although the "-se of such add t onal -ant'ties is, in someases, beneficial,

To illu'trate an emhod mmt or" our process wherein the alkil grop of thealkylating a ent and the alkyl gro p of th hydrocarbon ma:- nesiumhalide are difierent we cond cted a series of operations emp' oying theproc dure of Example III. wherein the lead remaininfrom the reaction of1057 parts of sodium-lead alloy with 167 parts of ethyl chloride wassuosequently reacted with 263 parts of n-propyl chloride, 16'? parts ofethyl chloride or 131 parts of methyl chloride paired with 57 4 parts ofethyl magnesium chloride. 66.5 parts of n-propylmagnesium chloride or57.4 parts of ethylmagne ium hlori e. respectively, each in 9 .9 partsof ether. Th s. in this example, wherein R and B were different, butwere both allzyl groups, yi1'S of 91.8, 86.9 and 78.2 per cent ofallzyllead prod ct based on the lead in the sodi m-lead alloy wereobtained, respectively. sim liarly. as examples of the proce s of ourinvention wherein the R and R of the above typical generalized eq ationwere the same or different, and one or both were aryl, we carried outoperations sim lar to Example III wherein theorganic hal d of the secondstage was 409 parts of nhenvl bromide emplo ed with either 118 parts ofphen lma ne iurn bromide or 57.4 parts of ethylma 'nes um chloride eachin 95.8 parts of ether, the yi l of product was 44.7 and 53.6 per centrespectively based on the lead in the sodiumlead allov. The arvlatingagent and arylmagnesium halide likewise can be em loyed in the onetareproc ss of Example I but the yield, altho gh m ch higher than thatobtained in the pr sent commm al process is somewhat lower than in our-referred t o-sta e embodiment.

As shown her tofo e it s not e sent al for the process of-o"r in nt onthat hloro alky ating and a vlat n a ents or hy rocar on-magnes m chlordes eemo oyed. A f rther ll strat on we reacted. 466 parts (it ethvl i de and 117 parts of ethl rn.a-"n ium iod de in 6 part of ether with thlea remain n from an o eration e m la E' 'amn II an accor ng to th furthr rocedure of that exam le. Th"re was obta ned 119 arts of product or ai ld of 4 5 p r c nt ba e on the l a ha ged a s d um lead a loy S m ar yu in 2% arts of eth l r mide and 862 parts of etL lmaene-s um brom e in9 .8 parts of eth r in the second stage, the e was obtained 119 narts ofr dict or a yield of 34. 5 rer. cent ba ed on the lead in th sodium-l adallo To llustrate that or th s s fil o rat on of the proce s of o r nention the ne ati e. or Y. group of the alk lat ng a ent. R'Y. and the X"r up of the h drmar n ma ne i m hal de RJ QX need n t he t e am e on-"ctr? a vo n it -"tn. "(A nh' r n g a 'pq afi" to he}: M E'v m"l* Therein the lead m V" arts J a a loy of the first stage was f l -owin r ant a rs r nn 5 .4 part" 0 st magnesium chlo e: 1.6? parts of hyl 'hlo'ide plus 117 a s glma ne m iodide: 4 parts of ethyl brom pl s 57 A carto et ma nefif m hlor e 31 "arts of triethvl pho phate plus 5 .4 parts ofeth ma nes m chloride. n each nstance n th res nce o .8 The yield ofproduct in the four Q operations was 125, 89.7, 129 and 59.? parts or ofproduct was 83.9 per cent based on the lead in the sodium-lead alloyemployed in the first stage.

The importance of the alkylating or arylating agent in combination withthe hydrocarbonmagnesium halide of our invention is shown in thefollowing series of operations. 'In one instance the procedure ofExample I was followed until the reaction between the ethyl chloride andthe sodium-lead alloy was complete, and the product was then dischargedfrom the autoclave and recovered. From 100 parts of sodium-lead alloywas obtained 31.2 parts of product, or a yield of 22.1 per cent based onthe lead in the sodiumlead alloy, which is normal for the presentcommercial process. In a second instance the procedure of Example IIIwas followed with ex- 1 ception that the ethyl chloride was notreintroduced along with the ethylmagnesium chloride and the ether. Afterthe subsequent operations described in Example III the yield of productfrom per cent based on the lead in the sodium-lead alloy, a result notsubstantially different from the yield obtained by the presentcommercial process. As shown in Example III by reintroducing the ethylchloride along with the ethyl-l L magnesium chloride and the ether ayieldof 117 parts of product or 83.5 per cent was obtained from the 100parts of sodium-lead alloy.

While the process of our invention is operable over a wide range oftemperatures and gives good results at temperatures as low as 0., wehave found that our preferred temperature is within the range of C. to85 C. When our two-stage reaction is employed it is sometimesadvantageous to operate the second stage at a different temperature thanthe first stage. However, temperatures preferably in the neighborhood of70 C. are employed in both the one-stage and twostage operations.

The amount of hydrocarbon-magnesium halide is not critical in theprocess of our invention. For example, in the manufacture oftetracthyllead we have obtained high efiiciency in the utilization ofthe ethylmagnesium chloride and good yields of product based on the leademployed when the ethylmagnesium chloride was used in amounts betweenabout 6 and parts per 100 parts of lead. Above this amount the yieldbased on lead is still high, but the improvement in yield based on theethylmagnesium chloride diminishes.

In general, the reaction of our process is completed within a few hours,i. e. to 8 hours. When it is coupled with the present sodium-lead alloymethod, we have found that a total time within the range ofapproximately to 6 hours is suflicient.

It is desirable to introduce the alkylating agent such as ethyl chlorideas a liquid. Therefore the autoclave is operated under a pressure sufii-12 cie'ntly high to maintain the fluid reactants in the liquid phase.Thus the pressure in the reaction vessel when using ethyl chloridepreferably is maintained Within the range of to 150 pounds per squareinch gauge.

For the process of our invention we have employed other alloys thansodium-lead alloy in either a oneor two-stage operation. Thus, employing100 parts of a calcium-lead alloy, having a composition corresponding tothe formula CaPb, with 300 parts of ethyl chloride in the first stage ofan operation similar to that of Example I, and in the second stage thesolution prepared from 14.7 parts of magnesium, 38.9 parts of ethylchloride and 89.8 parts of ether, we obtained 107 parts of product or ayield of 76.1 per cent based on the lead in the calcium-lead alloy.

Our process, in common with most of the processes of the prior art, whenemployed to make tetraethyllead also produced some hexaethyldilead. Itspresence is readily detected by noting the color in the final alkylleadproduct.-

If there is none present the color is water-white while a yellow colorindicates its presence. In

view of the widespread commercial use of tetraethyllead, it may bedesirable to convert hexaethyldilead to a more valuable product.Therefore any of the latter container in the final product can beconverted to tetraethyllead and free lead by heating. Actually, by suchheating, 82% by weight of tetraethyllead is formed and the free lead soproduced can be reprocessed. Further, most of the hexaethyldilead can beprevented from forming in our process by employing 100 parts of sodiumlead alloy was 81 parts, or 22 ("a temperatures near 85 C. or by lengthe time of the reaction at a lower temperature, say 70 C.

For the reaction of our invention to proceed effectively it is preferredthat the reaction zone be free from substantial amounts of certainmaterials which may be inert and which may act primarily as diluents.However certain materials when used in small concentrations are, in somecases, beneficial even though they do not directly improve the yields.For example, certain thermal stabilizers such as diisobutylene, styreneand naphthalene, when added in quantities of the order of a few per centbased on the lead, may be beneficial in reducing the tendency of thealkyllead compounds in the reaction mass to undergo thermaldecomposition. Further, certain known accelerators such as acetone,dipropyl lzetone, ethyl acetate, ethyl butyrate and butyl acetate maytend to accelerate the reaction when used in small quantities of theorder of .04 part to 1 part of lead. Excessive quantities should beavoided.

Hydrocarbons, such as commercial gasoline are additional examples ofmaterials which may be beneficial in small quantities, but harmful whenused in excess. The presence of such hydrocarbons in substantial amountstends to interfere with the progress of the alkylation reaction,particularly in the one-stage embodiment of our invention, althoughrelatively small amounts may be of some help. In general, as the amountof such hydrocarbons is increased, the yield of tetraalkyllead isreduced until finally little, if any, is produced.

Other embodiments of this invention can be made without departing fromthe spirit and scope of our invention which is not limited to thespecific embodiments given herein.

We claim:

1. A process for making tetrahydrocarbon- 5. A process for makingtetraethyllead comprising reacting lead with ethyl chloride andethylmagnesium chloride.

' 6. In a process for making a tetrahydrocarbonlead compound in whichboth alkyllead and free I lead is formed, the improvement comprisingreacting said free lead with an inorganic acid ester alkylating agentand an alkylrfn'agnesium halide compounds comprising reacting lead withan alkylating agent having the hydrocarbon radical in question andhaving a negative radical which reacts with magnesium and with analkylmagnesium halide.

3. A process for making tetrahydrocarbonlead compounds comprisingreacting a lead alloy with an alkylating agent having the hydrocarbonradical in question and having a negative radical which reacts withmagnesium and wit an alkylmagnesium halide.

4. A process for making a tetrahydrocarbonlead compound comprisingreacting lead with an inorganic acid ester alkylating agent having thehydrocarbon radical in question and having a negative radical whichreacts with magnesium and with an alkylmagnesium halide in which thehalide is selected from the group consisting of chlorine. bromine andiodine.

in which the halide is selected from the group consisting of chlorine,bromine and iodine.

7. A dual process for making tetraethyllead comprising treating a sodiumlead alloy with ethyl chloride, and reacting ethyl chloride and 1ethylmagnesium chloride'with the free lead so formed.

GEORGE CALINGAER'I. HYMIN SHAPIRO.

REFERENCES CITED The following references are of record in the file ofthis patent:

Calingaert, Chemical Reviews, vol. 2 (1925-6), p. 46.

Gilman, Organic Chemistry, An Advance Treatise, vol. 1, 2d ed., p. 500.John Wiley and Sons Inc. New York 1943.

7. A DUAL PROCESS FOR MAKING TETRAETHYLLEAD COMPRISING TREATING ASODIUM-LEAD ALLOY WITH ETHYL CHLORIDE, AND REACTING ETHYL CHLORIDE ANDETHYLMAGNESIUM CHLORIDE WITH THE FREE LEAD SO FORMED.